According to the prior art technique for fixing an insulating rod to an attachment fitting anchoring is usually accomplished by force fitting.
The resulting connection is very often unsatisfactory particularly because of the nature of the components to be associated, namely, a rod of insulating material and a metal attachment fitting.
More recently such connections have been attempted by bonding, the rod of insulating material being coated with a layer of bonding material or adhesive, but such attempts have been unsuccessful by reason of the formation of bubbles, thereby resulting in unsatisfactory anchoring which is unacceptable for industrial use.
Thus, U.S. Pat. No. 3,672,712 discloses a structure for connecting an attachment to the end of a fiberglass element. The end of the fiberglass element to be fixed to the attachment is divided into four equal segments. According to this patent a central opening is provided to facilitate the potting of the segments in resin.
German Pat. No. 1,074,688 discloses the fixing of a ceramic casing or envelop of an insulator to a core made of a plurality of fiberglass reinforced rods by means of a filler material (adhesive).
Swiss Pat. No. 571,267 discloses a method of anchoring the end of a rod of fibered reinforced synthetic resin in a fitting. According to this method the end of the rod is heated until weakening of the synthetic resin-fiber covering connection, enlarging in all directions and anchoring by filling the slots with synthetic resin which hardens.
French certificate of addition application U.S. Pat. No. 76 12787, publication No. 2,249,934, discloses a manner of connecting an anchoring fitting to a rod. A particular bonding method is used in which the bonding substance is introduced through hole which are then sealed off by stoppers.
German Pat. No. 1,259,531 discloses an insulator comprising a ceramic envelop or casing and a core or rod of fiberglass reinforced synthetic resin. The space between the core and the casing is filled with a liquid or pasty (bonding substance) medium. A locking member is applied against the rod to prevent it from turning.